Employee Retirement Benefit Plans - Components of Company's Net Periodic Benefit Costs (Detail) - USD ($) $ in Millions		3 Months Ended		9 Months Ended
		Mar. 31, 2017	Mar. 31, 2016	Mar. 31, 2017	Mar. 31, 2016	Jun. 30, 2016
Components of net periodic benefit cost:
Defined Benefit Plan, Service Cost		$ 0.8	$ 0.7	$ 2.4	$ 2.1
Defined Benefit Plan, Interest Cost		1.6	2.6	4.9	8.0
Defined Benefit Plan, Expected Return on Plan Assets		(2.7)	(2.4)	(8.1)	(7.5)
Defined Benefit Plan, Amortization of Gains (Losses)	[1]	(1.1)	(0.6)	(3.2)	(2.0)
Defined Benefit Plan, Net Periodic Benefit Cost		0.8	$ 1.5	2.4	$ 4.6
Estimated discounted value of future employer contributions		39.2		39.2		$ 39.3
Estimated annual cash contribution		$ 1.7		$ 1.7

[1] Amount represents the amortization of unrecognized actuarial gains/(losses).